From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-x243.google.com (mail-pf0-x243.google.com [IPv6:2607:f8b0:400e:c00::243]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3yMXcL37GPzDqlT for ; Thu, 26 Oct 2017 01:30:42 +1100 (AEDT) Received: by mail-pf0-x243.google.com with SMTP id b6so108584pfh.7 for ; Wed, 25 Oct 2017 07:30:42 -0700 (PDT) Date: Thu, 26 Oct 2017 00:30:20 +1000 From: Nicholas Piggin To: Michael Ellerman Cc: linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH] powerpc/64: set DSCR default initially from SPR Message-ID: <20171026003020.6ff970cf@roar.ozlabs.ibm.com> In-Reply-To: <874lqn1r89.fsf@concordia.ellerman.id.au> References: <20171024114444.13933-1-npiggin@gmail.com> <874lqn1r89.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, 25 Oct 2017 12:01:10 +0200 Michael Ellerman wrote: > Nicholas Piggin writes: > > > Take the DSCR value set by firmware as the dscr_default value, > > rather than zero. > > > > POWER9 recommends DSCR default to a non-zero value. > > > > From: Nicholas Piggin > > --- > > This has a problem that OS which set the DSCR to non-default > > then kexec to Linux will be used as our default. I send a > > corresponding patch to skiboot which resets SPRs in opal_reinit_cpus > > which will make this do the right thing in that case. > > That doesn't work for pseries etc. > > We should reset it in the kexec down path. Okay I'll add that too. We should have a hypercall to reset all the state for us like opal_reinit_cpus I reckon, but restoring it before kexec isn't a bad idea even if we had such a thing. Thanks, Nick